1. Field of the Invention
The present invention relates generally to a process for forming a solid hypochlorite precipitate on a fibrous substrate and the formed hypochlorite-releasing substrate. The process for forming a solid hypochlorite comprises the steps of: exposing one or more fibrous materials to an effective amount of aqueous alkaline earth salt solution, treating the fibrous material with an effective amount of hypohalite solution and allowing the alkaline earth salt solution to react with the hypohalite solution to form solid hypochlorite precipitate around the fibers in the fibrous material. The hypochlorite-releasing substrate may have a variety of uses, including but not limited to, cleaning wipes, dishwashing towels for hand use or in dishwashers, toilet bowl cleaning pads, bath and shower cleaning pads, laundry sheets for the washer or dryer, water filters, wound dressing materials, carpet stain removal pads, air deodorizer pads, food freshness substrates, air filtration substrates, and water disinfecting substrates. The composition and process for making the hypochlorite-releasing substrate enables the liquid phase to be removed from the substrate creating a stable hypochlorite-releasing substrate which is capable of rapid release of hypochlorite upon exposure to moisture or liquid.
2. Background of the Invention
There is a need for a stable cleaning and disinfecting substrate, such as a wipe or cleaning article that is capable of cleaning and removing residues from soiled surfaces while simultaneously destroying undesirable microorganisms, e.g. bacteria, mold, viruses, prions and the like that colonize on common surfaces with which people come into contact, such as door knobs, countertops, toilet seats, floors, beds, walls, and the like.
Hypohalite releasing compounds, such as the hypohalite and related compounds that release active forms of hypohalite and/or halogens, are extremely effective disinfectants capable of destroying a wide range of microorganisms. Hypohalite releasing antimicrobial compounds, and in particular the hypohalite, constitute a class of strong chemical oxidants possessing both cleaning and bleaching properties in addition to their antimicrobial properties making them superior to other disinfectants, such as quaternary ammonium biocides. The hypohalite class of chemical oxidants act to rapidly oxidize susceptible substances found in inorganic, organic and biological materials, rendering them more easily removed from surfaces, and in the case of colored or pigmented materials, bleaching them to white or colorless end products resulting in effective cleaning and stain removal from soiled surfaces. Owing to their strong oxidizing capability, hypohalite also posses inherent disinfection properties and additionally possess desirable characteristics including excellent aqueous solubility, mobility and a highly dissociative ionic nature. A further advantage of the hypohalite class with regard to disinfecting, is the speed and efficacy with which they attack microorganisms and either destroy them or render them non-viable following very short contact times. Yet a further advantage of the hypohalite is the wide susceptibility of many different types of microbial pests to their strong oxidizing potential and essentially the absence of any known microbe to develop an effective resistance against the action of these materials.
Typically, microbiologically contaminated surfaces seldom comprise only the microorganisms themselves, but include the presence of soils and other residues, including organic, inorganic and biological residues associated with the source of the microbiological contamination. These residues, including, for example, saliva, bodily is fluids, blood and common soils such as foods, oils and dirt, not only host microorganisms, but can act to shield and protect the microorganisms from the disinfectant action of non-hypohalite disinfectant materials.
One seeming disadvantage of the hypohalite class of materials is their susceptibility to decomposition, including self-decomposition and reactive decomposition owing to the interaction of the hypohalite with the substrates and materials, which they contact during packaging and storage. Particularly in the case of pre-wetted wipes, the disinfecting hypohalite composition is impregnated onto and interacts with the absorbent carrier substrate during storage. Hence, freshly prepared solutions or disinfectant articles utilizing these materials are typically required to ensure adequate activity for ensuring effective disinfection of surfaces. Attempts have been made in the past to provide a convenient disinfectant article by loading a liquid hypohalite solution onto an absorbent substrate such as a wipe. One of the problems with pre-loaded bleach wipes is that they lack sufficient stability to ensure suitable disinfecting efficacy at time of use, particularly following typical storage times and/or less than ideal storage conditions representative of real world environments encountered in the home, office, business, hospital or field where needed.
Another prior art embodiment of hypohalite loaded substrate which has been used previously is a dry substrate which is loaded with a solid hypohalite which is adhered to the substrate using a binder or adhesive agent. The problems with these dry loaded solid hypohalite substrates is that the solid hypohalite may only be loaded on the exterior of the surface of the substrate rather than evenly distributed throughout the substrate, the adhesive agent or binder may interferes with the quick release of the hypohalite, and if the particles size of the solid hypohalite is too large then the release rate may be too slow, but if the particles are too small the particles will fall off the substrate too easily and will not be delivered to the desired point of use.
3. Description of the Related Art
The prior art covers numerous types of cleaning substrates and compositions with hypochlorite. Wet cleaning wipes loaded with hypochlorite are know in the art and cleaning tools with pad loaded with a particulate hypochlorite which is adhered to the surface of the pad with a binder or adhesive are also well-known in the art. In addition, there are also solid tablets which include a solid hypochlorite which are commonly used in toilet bowl cleaning tablets. Furthermore, there are numerous processes for the formation of hypochlorite which are also described in the prior art. None of the prior art references describe a process for making a solid hypochlorite precipitate on a nonwoven substrate or a fibrous substrate where the solid hypochlorite is formed on the substrate as a precipitate.
U.S. Pat. No. 7,008,600 to Kastigras et al. discloses a cleaning composition containing hypohalite and surfactant on a nonwoven substrate forming a wet cleaning wipe or pad. In the case of the Kastigras invention, the cleaning composition with the hypohalite and surfactant is formed and then it is loaded onto the nonwoven substrate. In addition, the disinfecting article of Kastigras is in a wet form on the substrate and must be stored in a sealable housing to ensure the stability of the substrate with the hypohalite solution. Unlike the present invention, the disinfecting article taught by Kastigras contains a hypohalite cleaning composition that is formed prior to being added to the nonwoven substrate and the disinfecting article is loaded with an aqueous solution of hypohalite and surfactant. The use of a wet wipe loaded with an aqueous solution of hypochlorite is less desirable than having a wipe with the liquid phase removed because there are stability and degradation problems that necessitate the use of a sealable housing.
U.S. Pat. No. 6,916,480 to Anderson et al. describes a wipe with controlled-release of antimicrobial agents which may include calcium hypochlorite particles. Similarly, U.S. Pat. No. 6,734,157 to Radwanski, et al. teaches a controlled-release wipe which may contain calcium hypochlorite particles adhered to the surface of the wipe. The antimicrobial wipe taught by Anderson utilizes a polymer mixture to control the release rate of the antimicrobial agent loaded on the wipe. In the case of Anderson and Radwanski, the antimicrobial wipes are formed by adhering solid particles of calcium hypochlorite to the surface of the wipe with an adhesive or binding agent. Anderson does not teach a process for forming a solid hypochlorite precipitate on a fibrous material in the absence of a binder or adhesive. One of the deficiencies of this type of substrate where a solid bleach particle is adhered to the substrate is that the adhesive and/or the larger particle size prevent rapid release of the hypochlorite when it is exposed to moisture or liquid. If less adhesive is used or small particle size hypochlorite is used then there is a problem with dusting because the particles will not all stay on the substrate prior to use. In addition, the antimicrobial wipe taught by Anderson has solid hypochlorite particles on the surface of the wipe rather than solid hypochlorite precipitate formed around the fibers of the fibrous substrate, as in the present invention. In addition, the invention of Anderson requires that the hypohalite particles are on the surface of the wipe, whereas the present invention allows the hypohalite precipitate to be substantially evenly distributed throughout one or more layers of the substrate material.
The use of a particulate form of solid hypochlorite adhered to the surface of the substrate is less desirable than the present invention because a binder or adhesive is necessary which adds additional expense. In addition, to make the solid calcium hypochlorite particles adhere to the surface of the wipe they cannot be so fine that they fall off the surface of the substrate leading to dusting or exfoliation. Unfortunately, particles that are large enough to effectively adhere to the surface of the substrate means there is less surface area exposed to moisture or fluid which means a slower release rate of hypochlorite than that of the present invention.
U.S. Pat. No. 4,513,459 to Doughty describes a bleach cake in a filter sleeve which is used in toilet bowl tanks to clean and disinfect. The bleach cake in Doughty comprises a solid calcium hypochlorite and the filter sleeve surrounds the bleach cake to prevent particles from the cake breaking off and obstructing flow of the water into the toilet bowl from the tank. The invention of Doughty differs from the present invention because the bleach cake is formed as a separate solid material that is then encased in the filter sleeve whereas the present invention involves the formation of a solid hypochlorite precipitate around the fibers of a fibrous substrate.
The prior art references teach wet loaded hypochlorite containing wipes which have stability and degradation problems unless they are stored in sealable containers which do not allow light or air exposure. The prior art also teaches wipes loaded with solid particulate calcium hypochlorite particles using an adhesive or binder which have the added expense of an adhesive and do not release hypochlorite as efficiently as the present invention. In addition the prior art also teaches bleach cakes, but these bleach cakes are not formed on a fibrous substrate and are primarily a solid bleach rather than a combination of solid bleach and fibrous material. In addition, there are references about the formation of calcium hypochlorite but none which talk about hypochlorite formation on a fibrous substrate. In view of the prior art, there is a need for a process for forming a solid hypochlorite precipitate on a fibrous substrate and a hypochlorite releasing substrate that overcomes the disadvantages and shortcomings associated with prior art processes and hypochlorite releasing substrates.